1. Field of the Invention
This invention relates generally to baffle and switch control in a refrigerator, and more particularly, to a unitary baffle and switch control assembly that is motor driven in a response to frozen food and fresh food compartment temperatures and to defrost commands.
2. Summary of the Invention
In typical domestic refrigerators, a fresh food compartment and frozen food compartment separated from each other by a divider wall are cooled by a common compressor-condenser-evaporator system. The frozen food compartment is chilled to sub-freezing temperatures by a fan forcing air past the evaporator in the compartment. The fresh food compartment in turn is cooled by chilled freezer compartment air passing through a baffle in the divider wall.
Commonly, the temperature of the frozen food compartment is controlled directly by thermostat or microprocessor based cycling of the compressor to bring the frozen food compartment to its temperature set point. The temperature of the fresh food compartment in turn is controlled indirectly by operating the baffle to pass chilled frozen food compartment air through the divider wall into the fresh food compartment. When either compartment requires cooling, the evaporator fan is operated. During defrost, a defrost heater associated with the evaporator is energized and the baffle is closed.
Prior art controls require a baffle that is solenoid or bellows operated and further require relays or triacs to operate the compressor, fan and defrost heater. These controls accordingly are relatively complex, expensive and prone to failure. Furthermore, the continuous energization of relays or triacs whenever a load is energized adds undesirable heat to the compartment in which the devices are located. This heat must be removed by the refrigeration system, requiring yet an additional expenditure of energy. There currently exists a need to simplify and make more reliable and efficient the control of compartment temperatures and defrost operation in refrigerators.
In accordance with the invention, temperature control in multiple compartment refrigerators is simplified and made more reliable by a unitary control assembly comprising a cam mechanism that is linked to the baffle and has a profiled control surface adjacent a number of electric switches for operating the compressor, evaporator fan and defrost heater. As the cam is rotated by an electric motor to predetermined angles of rotation in response to output commands from a microprocessor or other control device, the baffle is indexed between its open and closed positions and the switches operated to defrost the frozen food compartment and cool the two compartments to the desired temperatures.
In accordance with another aspect of the invention, the baffle comprises a stationary baffle plate formed with an array of through slots together with a movable baffle plate having a corresponding array of through slots. The two plates are retained in parallel with each other, whereby sliding of the moveable plate across the stationary plate indexes the baffle open or closed. The movable baffle plate is formed with a T-shaped slot which is coupled to a pin formed on the cam at a position offset from its center of rotation. With the compressor, evaporator fan and defrost heater switches spaced circumferentially around the control surface of the cam, operation of the switches and baffle is synchronized to provide the desired frozen food and fresh food compartment temperatures as the cam is rotated by the cam motor.
In accordance with another aspect of the invention, the positions of the compressor, evaporator fan, and defrost heater switches around the perimeter of the cam are chosen to facilitate flexible operation of the unitary control assembly to energize whatever device is required by the conditions sensed within the refrigerator compartments. Most advantageously, this flexibility of operation is accomplished without imposing any unnecessary loads e.g., on the compressor, even temporarily, while the cam is being rotated from one position to another. Such unnecessary loads are particularly onerous in the case of a refrigeration compressor which will become overstressed if not provided a minimum off period between periods of operation.
In accordance with yet another aspect of the invention, a unitary control assembly that is capable of energizing the compressor, evaporator fan and defrost heater of a refrigerator is provided that will dissipate substantially no heat energy while energizing these devices. The only time that the control assembly dissipates heat energy is when the cam motor is energized to make a change in operating states of the refrigerator.
Accordingly, one object of the invention is to provide an improved baffle and switch control in a multiple compartment refrigerator that is economically produced and reliably operated.
Another object is to provide a unitary control assembly for efficiently operating the compressor, evaporator fan, defrost heater and baffle in a multiple compartment refrigerator.
A further object is to provide a unitary control assembly in a refrigerator for establishing desired frozen food and fresh food temperatures by operating the baffle, compressor and evaporator fan synchronously in response to commands from a separate control unit.
Other objects and advantages of the present invention will become apparent from the following detailed description thereof made with reference to the accompanying drawings which form a part of the specification.